M’s, A’s set to open four-game series

OAKLAND, Calif. — Two teams that have taken their shots at the first-place Houston Astros turn their attention to second place in both the American League West and AL wild-card races when the Seattle Mariners and Oakland Athletics open a four-game series Thursday night.

Mariners left-hander Wade LeBlanc (7-3, 3.92 ERA) is scheduled to open the series against A’s right-hander Frankie Montas (5-3, 3.75), who will be promoted from Triple-A in order to make the start.

The Mariners (74-59) got within 3 1/2 of first place before losing back-to-back home games to the Astros last week to fall 5 1/2 back.

Two costly losses at San Diego the last two days have dropped the Mariners a full eight behind Houston.

The A’s (80-54), meanwhile, lost two of three at Houston in a series that ended with a 5-4, walk-off defeat Wednesday afternoon that put them 2 1/2 back of the Astros (82-51).

Surely, the Mariners enter the Oakland series far more desperate than the A’s, who currently hold the second wild-card position, a full 5 1/2 games ahead of Seattle. The clubs still meet seven times, including three at Seattle in the final week of the season.

The Mariners currently hold a 7-5 advantage in the season series.

LeBlanc paved the way for one of those wins over Oakland, throwing four shutout innings in a 4-1 home win on May 3. He’s 2-0 with a 4.21 ERA in six career meetings with the A’s, including four starts.

Montas finds himself back in the Oakland rotation for the first time since July 29 because of recent injuries suffered by Sean Manaea and Brett Anderson.

He hasn’t faced the Mariners this season and has never started against them, posting a 0-0 record and 4.15 ERA in three career relief appearances.

With Daniel Mengden, another starter who has bounced back and forth from Triple-A, a possible replacement for Anderson on Saturday, Oakland figures to have to count upon its revamped bullpen more than usual.

Thanks to the trade-deadline (and beyond) acquisitions of Jeurys Familia, Fernando Rodney and Shawn Kelley, the A’s have turned into a club that has counted upon the bullpen almost as much as the starters in recent games.

Kelley has been the surprise of the group, having fallen out of favor in Washington before being snatched up by Oakland for next to nothing.

He’s pitched 10 times for the A’s, allowing no runs and two hits in 8 2/3 innings with two walks and nine strikeouts.

“We used him a little differently early on, more clean innings, and now we’re using him in leverage spots,” A’s manager Bob Melvin praised. “He’s been a chameleon in terms of his ability to pitch in different spots for us.”

The Mariners also have bolstered their relief corps for the stretch run, promoting their Triple-A closer, Shawn Armstrong, to serve as one of Edwin Diaz’s set-up men.

Armstrong did not allow a run in 25 of his last 26 appearances for Tacoma. He then pitched a scoreless eighth inning in Tuesday’s 2-1 loss at San Diego in his Mariners debut.